The present invention relates to methods and apparatus for conducting and promoting the propagation and growth, under conditions of substantially zero gravity, of micro-organisms. The term micro-organisms is employed herein as including, for example, cells, molds, yeasts, protozoa, bacteria, and viruses. The term cells is to be understood to include tissues from which the cells are derived, as well as the cells themselves. The invention is concerned primarily with the production or biosynthesis of the metabolic products of the micro-organisms, such products including substances of therapeutic or industrial importance, such as, for example, enzymes, antibiotics, amino acids, vitamins, hormones, and vaccines.
It has been recognized in the prior art that the sustained growth of micro-organisms is limited by the accumulation of toxic metabolites or catabolites, and by the depletion of nutrients in the culture media. In any culture system, in order to prevent the rate of organism proliferation from dropping to zero, fresh growth medium must be supplied at a proper and steady rate so that optimal organism concentration may be maintained by removal of toxic metabolitic products, replenishing necessary nutrients, and removing the products of the fermentation or other growth process, in proportion to their rate of formation. Under earth conditions, these limitations have usually been controlled by the use of various filtration devices, but these have the drawback of low capacity and may readily become clogged.
Data from Biosatellite II experiments have shown that cultures of bacteria grown in a liquid medium under zero gravity conditions in space produce significantly larger populations of bacteria than identical cultures grown on earth. This suggests that fermentation or other analogous growth processes conducted under conditions of zero or near-zero gravity offer a potential for the production of important biologicals or therapeutic substances on a commercial scale with greatly enhanced yield potential in a space vehicle in orbital flight. Under these conditions, advantage is taken of weightlessness to maximize production of the desired products.
The use of a space vehicle for the manufacture of hollow ball bearings and other industrial metal products is proposed in U.S. Pat. No. 3,534,926, and pertinent apparatus is described therein. In U.S. Pat. No. 3,396,084, there is disclosed a test chamber for monitoring the growth and metabolism of cells under zero gravity conditions, but no examples of specific organisms or fermentation processes are mentioned.